Recent epidemiological reports have suggested an excess morbidity or mortality from leukemia among male workers in electrical occupations. There is little biological evidence to suggest why electrical workers might have an extra risk of leukemia. There is, however, good evidence that certain pulsed electromagnetic fields (EMF) accelerate bone or wound healing. The biological basis of this phenomenon is also not understood. For the latter case, it has been suggested that alteration of cell membrane structure and/or receptor sites for hormones and other growth factors may be involved. Since cell membrane integrity is important in the functional response of cells of the immune system, we are looking for some possible common parameters that may account for both biological phenomena, that is, enhanced leukemia and accelerated bone and wound healing. Utilizing two parameters of the immune system, we are investigating the influence of EMF on macrophage chemotaxis and on T cell blastogenesis. In both instances, we note some inhibitory effects brought about by 5.2 msec bursts of bipolar repeat 15 HZ bursts of energy.